A kind of iron ion enhanced aramid nanofiber film and preparation method thereof

Abstract

The invention provides an aramid nanofiber film reinforced with iron ions and a preparation method thereof. The method comprises the following steps: dissolving FeCl3·6H2O in dimethyl sulfoxide, then adding para-aramid fiber, KOH and deionized water and mixing them uniformly, wherein the mass ratio of FeCl3·6H2O, para-aramid fiber and KOH is (0.02-0.1):1:(1.3-1.7), so as to obtain a dispersion; pouring deionized water into the dispersion and stirring uniformly, wherein the volume ratio of deionized water to the dispersion is (95-105):25, so as to obtain a suspension; draining the liquid in the suspension, then cold pressing and drying in sequence, so as to obtain the aramid nanofiber film reinforced with iron ions, and greatly improving the mechanical properties and insulation properties of the aramid nanofiber film.

Description

Technical Field

[0001] The present invention relates to an aramid nanofiber film, in particular to an iron ion-reinforced aramid nanofiber film and a preparation method thereof Background Art

[0002] The full name of aramid fiber is aromatic polyamide fiber, which is called Aramid fiber in English (DuPont's trade name Kevlar is a type of aramid fiber, namely para-aramid fiber). It has extremely high strength and modulus, as well as excellent properties such as high temperature resistance, acid and alkali resistance, and light weight, and is widely used in the aviation industry.

[0003] Aramid nanofibers (ANFs) are prepared by separating large-sized para-aramid fibers in a mixture of dimethyl sulfoxide (DMSO) and potassium hydroxide. ANFs are widely used to enhance the strength of polymer materials due to their nano-effect and retention of the molecular structure of Kevlar. However, the mechanical stress of polymer-based composite films formed by ANFs as fillers (in small amounts) cannot exceed that of pure ANF films. For example, it has been reported that the tensile stress of pure ANF films is 191 MPa, which is much higher than that of most polymer-based composite films using ANFs as fillers.

[0004] In order to make full use of the mechanical properties of ANF-based composite films and expand their application areas, further improving the mechanical properties of ANF-based composite films has attracted great attention in scientific and technological work. At present, the mechanical properties of ANF-based composite films are usually improved by introducing polymers or 2D inorganic materials. For example, flexible polymers polyvinyl alcohol and polyurethane do not have the good reinforcement effect of inorganic fillers (inorganic fillers have high strength and excellent performance), and cannot enhance the insulation properties of the film. Carbon nanotubes and graphene have a good reinforcement effect, but due to their own rigidity, excessive addition will cause more damage to the toughness of the film, and it is easy to aggregate. Poor dispersion will damage the mechanical properties of ANF-based composite films. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides an iron ion reinforced aramid nanofiber film and a preparation method thereof, which greatly improves the mechanical properties and insulation properties of the aramid nanofiber film.

[0006] The present invention is achieved through the following technical solutions:

[0007] A method for preparing an iron ion-reinforced aramid nanofiber film comprises the following steps:

[0008] S1, dissolving FeCl3·6H2O in dimethyl sulfoxide, then adding para-aramid fiber, KOH and deionized water and mixing evenly, the mass ratio of FeCl3·6H2O, para-aramid fiber and KOH is (0.02-0.1):1:(1.3-1.7), to obtain a dispersion;

[0009] S2, pouring deionized water into the dispersion and stirring evenly, the volume ratio of deionized water to the dispersion is (95-105):25, to obtain a suspension;

[0010] S3, draining the liquid in the suspension, followed by cold pressing and drying in sequence to obtain an iron ion reinforced aramid nanofiber film.

[0011] Preferably, in S1, the ratio of FeCl3·6H2O to dimethyl sulfoxide is (0.02-0.1) g:500 mL.

[0012] Further, in S1, FeCl3·6H2O is first added to dimethyl sulfoxide, then heated to 50-60°C, stirred for 30-45 min, and then para-aramid fiber, KOH and deionized water are added.

[0013] Preferably, in S1, the ratio of KOH to deionized water is (1.3-1.7) g: (4-6) mL.

[0014] Furthermore, after adding para-aramid fiber, KOH and deionized water to S1, magnetic stirring was performed at room temperature for 45 to 50 h to obtain a deep red dispersion.

[0015] Preferably, S1 dissolves FeCl3·6H2O in dimethyl sulfoxide, and then sequentially adds para-aramid fiber, KOH and deionized water.

[0016] Preferably, in S3, the suspension is subjected to vacuum-assisted filtration, followed by cold pressing and drying.

[0017] Furthermore, the cold pressing described in S3 is performed for 50 to 70 seconds.

[0018] Furthermore, the drying described in S3 is performed at 100 to 110° C. for 6 to 10 minutes.

[0019] An iron ion reinforced aramid nanofiber film obtained by any one of the above methods for preparing an iron ion reinforced aramid nanofiber film.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] The invention discloses a method for preparing an aramid nanofiber film enhanced by iron ions. In an alkaline environment provided by deionized water, DMSO and KOH, iron ions are combined with hydroxide ions to separate iron hydroxide nanoparticles, and then iron metal ions are introduced into the aramid fiber cracking process by in-situ growth, so that they are deposited into metal nanoparticles uniformly attached to the surface of the aramid nanofibers, and then deionized water is added and stirred uniformly. Through this reduction and protonation process, the enhanced aramid nanofibers are precipitated from dimethyl sulfoxide and transferred to deionized water, and the liquid in the suspension is drained, and then cold pressed and dried to form a solid iron ion enhanced aramid nanofiber film. In the iron ion enhanced aramid nanofiber film, the iron metal enhances the interface bonding of the aramid nanofiber itself through coordination and electrostatic interaction, as well as the high strength and high modulus inside the iron hydroxide nanoparticles, thereby greatly improving the mechanical properties and insulation properties of the aramid nanofiber film. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a cross-sectional view of a pure aramid nanofiber film with a scale bar of 10 μm.

[0023] Figure 2 This is a cross-sectional view of a pure aramid nanofiber film with a scale bar of 1 μm.

[0024] Figure 3 This is a cross-sectional view of the aramid nanofiber film with iron ion-assisted cleavage according to Example 1 of the present invention at a scale of 110 μm.

[0025] Figure 4 This is a cross-sectional view of the aramid nanofiber film with iron ion assisted cleavage according to Example 1 of the present invention at a scale of 1 μm.

[0026] Figure 5 This is a diagram of the mechanical properties of the pure aramid nanofiber film and the aramid nanofiber film doped with iron ions in Example 1.

[0027] Figure 6 This is a diagram of the dielectric insulation performance of the pure aramid nanofiber film and the aramid nanofiber film doped with iron ions in Example 1.

[0028] Figure 7 The present invention is a flow chart for preparing the iron ion-reinforced aramid nanofiber film. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0030] The present invention provides a method for preparing an iron ion-reinforced aramid nanofiber film, such as Figure 7 As shown, the specific steps include:

[0031] Step 1, adding 0.02-0.1 g of metal salt FeCl3·6H2O to 500 mL of dimethyl sulfoxide, then heating to 50-60° C., and stirring for 30-45 min to completely dissolve it, to obtain a dimethyl sulfoxide solution of FeCl3;

[0032] Step 2: 1g PPTA (poly(p-phenylene terephthalamide), also known as para-aramid fiber, Figure 7 aramid fiber), 1.3-1.7 g KOH and 4-6 mL deionized water were added to the solution prepared in step 1 in sequence, and magnetically stirred at room temperature for 45-50 h to obtain a dark red ANF dispersion;

[0033] Step 3, pour 95-105 mL of deionized water into 25 mL of ANF dispersion and stir evenly, and aramid nanofibers are precipitated through this reduction protonation process (transferred from dimethyl sulfoxide to deionized water).

[0034] Step 4, the suspension obtained in step 3 is subjected to vacuum-assisted filtration to drain the liquid, followed by cold pressing for 50 to 70 seconds and drying at 100 to 110° C. for 6 to 10 minutes to form a solid nanofilm, i.e., an iron ion-reinforced aramid nanofiber film.

[0035] In the following examples, FeCl3·6H2O in step 1 accounted for 2%, 5% and 10% of the solution mass respectively, and all solid nanofilms were named Fe 3+ / ANF-n, where n represents the percentage of FeCl3·6H2O in the solution mass.

[0036] Example 1

[0037] The present invention provides a method for preparing an iron ion-reinforced aramid nanofiber film, which specifically comprises the following steps:

[0038] Step 1, adding 0.02 g of metal salt FeCl3·6H2O to 500 mL of dimethyl sulfoxide, then heating to 50°C and stirring for 30 minutes to completely dissolve it, to obtain a dimethyl sulfoxide solution of FeCl3;

[0039] Step 2, 1.0 g PPTA, 1.5 g KOH and 5 mL deionized water were added to the solution prepared in step 1 in sequence, and magnetically stirred at room temperature for 48 h to obtain a deep red ANF dispersion;

[0040] Step 3: Pour 100 mL of deionized water into 25 mL of ANF dispersion to precipitate aramid nanofibers through the reduction and protonation process.

[0041] Step 4: The suspension obtained in step 3 was drained by vacuum assisted filtration, cold pressed for 1 min, and dried at 105 °C for 8 min to form a solid nanofilm named Fe 3+ / ANF-2.

[0042] Example 2

[0043] The present invention provides a method for preparing an iron ion-reinforced aramid nanofiber film, which specifically comprises the following steps:

[0044] Step 1, add 0.05 g of metal salt FeCl3·6H2O to 500 mL of dimethyl sulfoxide, then heat to 50°C and stir for 30 minutes to completely dissolve it, to obtain a dimethyl sulfoxide solution of FeCl3;

[0045] Step 2, 1.0 g PPTA, 1.5 g KOH and 5 mL deionized water were added to the solution prepared in step 1 in sequence, and magnetically stirred at room temperature for 48 h to obtain a deep red ANF dispersion;

[0046] Step 3: Pour 100 mL of deionized water into 25 mL of ANF dispersion to precipitate aramid nanofibers through the reduction and protonation process.

[0047] Step 4: The suspension obtained in step 3 was drained by vacuum assisted filtration, cold pressed for 1 min, and dried at 105 °C for 8 min to form a solid nanofilm named Fe 3+ / ANF-5.

[0048] Example 3

[0049] The present invention provides a method for preparing an iron ion-reinforced aramid nanofiber film, which specifically comprises the following steps:

[0050] Step 1, adding 0.1 g of metal salt FeCl3·6H2O to 500 mL of dimethyl sulfoxide, then heating to 50°C and stirring for 30 minutes to completely dissolve it, to obtain a dimethyl sulfoxide solution of FeCl3;

[0051] Step 2, 1.0 g PPTA, 1.5 g KOH and 5 mL deionized water were added to the solution prepared in step 1 in sequence, and magnetically stirred at room temperature for 48 h to obtain a deep red ANF dispersion;

[0052] Step 3: Pour 100 mL of deionized water into 25 mL of ANF dispersion to precipitate aramid nanofibers through the reduction and protonation process.

[0053] Step 4: The suspension obtained in step 3 was drained by vacuum assisted filtration, cold pressed for 1 min, and dried at 105 °C for 8 min to form a solid nanofilm named Fe 3+ / ANF-10.

[0054] Figure 1 This is a cross-sectional view of a pure aramid nanofiber film (i.e., no FeCl3·6H2O is added in step 1 of Example 1, and the rest remains unchanged) with a scale of 10 μm. Figure 2 This is a cross-sectional view of a pure aramid nanofiber film at a scale of 1 μm. Figure 1 and Figure 2 It can be seen that the fracture surface of the pure aramid nanofiber film is neat, almost brittle fracture, and no nanosheet extraction phenomenon is visible.

[0055] Figure 3 It is a cross-sectional view of the aramid nanofiber film with iron ion-assisted cleavage according to Example 1 of the present invention at a scale of 110 μm. Figure 4 This is a cross-sectional view of the aramid nanofiber film with an iron ion-assisted cleavage according to Example 1 of the present invention at a scale of 1 μm. Figure 3 and Figure 4 It can be seen that there is obvious fiber extraction between the layers of the aramid nanofiber film doped with iron ions than between the layers of the pure aramid nanofiber film, which proves that the doping of iron ions in the form of iron hydroxide nanoparticles enhances the interfacial bonding of the aramid nanofibers themselves, thereby enhancing the mechanical properties of the aramid nanofiber film.

[0056] Figure 5 Figure 1 is a graph showing the mechanical properties of a pure aramid nanofiber film and an aramid nanofiber film doped with iron ions in Example 1. Figure 5 It can be seen that the mechanical strength of pure aramid nanofiber film can reach 172MPa, while the mechanical strength of aramid nanofiber film doped with iron ions can reach 314MPa, and the mechanical strength of aramid nanofiber film doped with iron ions is enhanced by 83%.

[0057] In addition, the elongation at break of pure aramid nanofiber film can reach 17.7%, while the elongation at break of aramid nanofiber film doped with iron ions can reach 29.2%. The elongation at break of aramid nanofiber film doped with iron ions increased by 65%, indicating that iron ion doping can improve the mechanical properties of aramid nanofiber film.

[0058] Figure 6The dielectric insulation performance diagram of the pure aramid nanofiber film and the aramid nanofiber film doped with iron ions in Example 1. The insulation performance of the corresponding film is evaluated by testing the dielectric breakdown strength. When the film is broken down, its breakdown voltage is recorded. Each film is tested 10 to 15 times. The breakdown voltage divided by the film thickness is the breakdown strength. 10 groups of data are selected to obtain 10 breakdown strengths. The two-parameter Weibull cumulative probability function is used for analysis to determine the value with the highest probability. Therefore, it can be concluded that the insulation performance of the pure aramid nanofiber film is 41.3 kV mm -1 The insulation performance of the aramid nanofiber film doped with iron ions in Example 1 is 65.1 kV·mm -1 .

Claims

1. A method for preparing an iron ion-reinforced aramid nanofiber film, characterized in that: The steps include: S1, dissolving FeCl3·6H2O in dimethyl sulfoxide, the ratio of FeCl3·6H2O to dimethyl sulfoxide is (0.02-0.1) g: 500 mL, then adding para-aramid fiber, KOH and deionized water in sequence and mixing evenly, the mass ratio of FeCl3·6H2O, para-aramid fiber and KOH is (0.02-0.1): 1: (1.3-1.7), to obtain a dispersion; S2, pouring deionized water into the dispersion and stirring evenly, the volume ratio of deionized water to the dispersion is (95-105):25, to obtain a suspension; S3, vacuum-assisted filtration of the suspension, followed by cold pressing and drying in sequence, the cold pressing being performed for 50 to 70 seconds to obtain an iron ion-reinforced aramid nanofiber film.

2. The method for preparing the iron ion enhanced aramid nanofiber film according to claim 1, characterized in that: In S1, FeCl3·6H2O is first added to dimethyl sulfoxide, then heated to 50-60°C, stirred for 30-45 min, and then para-aramid fiber, KOH and deionized water are added in sequence.

3. The method for preparing the iron ion enhanced aramid nanofiber film according to claim 1, characterized in that: In S1, the ratio of KOH to deionized water is (1.3-1.7) g: (4-6) mL.

4. The method for preparing the iron ion enhanced aramid nanofiber film according to claim 3, characterized in that: After adding para-aramid fiber, KOH and deionized water, S1 was magnetically stirred at room temperature for 45 to 50 h to obtain a deep red dispersion.

5. The method for preparing the iron ion enhanced aramid nanofiber film according to claim 1, characterized in that: The drying described in S3 is performed at 100 to 110° C. for 6 to 10 minutes.

6. An iron ion reinforced aramid nanofiber film obtained by the preparation method of the iron ion reinforced aramid nanofiber film according to any one of claims 1 to 5.

Images